If the sight at zeroing has been calibrated for a distance from the weapon (sight) to the target of 100 m the ballistic curve of the projectile and the sight line will intersect at the distance 100 m. At very short range (up to 20 m, depending on the distance between the weapon barrel of the and the sight), the ballistic curve will pass under the sight line; between 20 m and 100 m, the ballistic curve will pass over the sight line, whereas the ballistic curve will pass under the sight line at distances longer than 100 m.
It is desired to compensate automatically for said deviation at other distances than that the sight has been calibrated for by zeroing. However, weapons are used not only for shooting more or less horizontally but also for shooting at an angle upwards or, more often, downwards e.g. from a helicopter. Also a moving target may be aimed at. It is therefore desired to adjust the sight automatically not only for the different distances to the target but also in dependence of the different parameters involved in sighting under the conditions mentioned. At the present state of the art miniature range finders of infrared type as well as miniature angular gauges are available. The present state of the art also includes binoculars with integrated compass. Measurement of the direction in which the shooter is aiming in combination with measurement of the distance to a moving target enables calculation of the speed at which the target moves. Alternatively, the speed can be measured by GPS (global positioning system). With the parameters easily available the aiming point can be controlled in dependence thereof in order to have the weapon directed in different positions towards a target, even towards a moving target, located at different distances from the shooter. However, control of the aiming point by mechanical adjustment thereof to different positions in different directions in dependence of said parameters involves great complications.